1. Field of the Invention
The present invention falls within the medical field, especially in the operating methodology when preparing and conducting surgical operations.
The invention specifically relates to anatomical medical imaging, in order to perform robotic-assisted surgical operations.
The present invention will find a preferred, but in no way restricted, application to surgical operations of the anatomical region of the rachis.
To this end, the invention relates to a device for positioning a surgical instrument relative to the body of a patient.
It should be noted that the invention will be described according to a specific example of operation at the level of the lumbar rachis, the level of the anterior curvature of the lordosis of the spine. However, the invention can be used for an operation at the level of the upper and lower cervical rachis, the back or thoracic rachis, as well as the sacral rachis and the coccyx.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
In this anatomical area, surgical procedures are delicate, thorough and risky operations that require accurately drilling, breaking or milling a vertebra, dissecting muscles, ligaments, vertebral discs, while avoiding damaging the spinal cord, the nerve roots, the veins and the nerves.
For example, the commonly performed procedures include laminectomy, radicular release, in the cases of lumbar spinal stenosis or a herniated disc; arthrodesis consisting in combining vertebrae by screwing into a pedicle, kyphoplasty and vertebroplasty consisting in injecting a cement into the vertebral body.
Such operations are implemented through an as narrow as possible operating channel, in order to reduce hospitalization and facilitate the patient's recovery, even more through a minimally invasive or percutaneous surgery. The narrowness of this operating channel makes the precision of the operation by the practitioner difficult, since the visibility decreases due to bleeding. In this condition, a rate of misplacement of pedicle screws up to 25% results, knowing that the aggressive misplacements make up 3 to 5%.
In order to improve the accuracy of his operation, the surgeon now uses anatomical medical imaging systems, in particular fluoroscopy and navigation.
First of all, fluoroscopy generates X-rays over a period permitting to acquire images continuously and thus achieve a direct view, where the surgeon can monitor in real time the progress of his tool within the anatomical structure. However, since extended or repeated exposure to these ionizing radiations is harmful to the medical personnel and the patient, the use of this technique is deliberately limited.
On the other hand, navigation permits to view a virtual tool on a pre- or per-operative imaging, on which the surgeon observes in real time the progress of his tool, even more so in the case of a three-dimensional (3D) navigation.
However, a first drawback arises from the complexity of the calculations of for positioning the surgical tools, leading to approximations and causing wrong positioning. In addition, the existing techniques require positioning a fixed marker on the patient's body, presently invasively screwed into the spine, for example, and to which the image-acquisition optics of the navigation system is pointed.
Furthermore, these techniques do not permit to cope with the errors related to the manual performance of the surgical procedure by the practitioner, in particular in the case of a stressing step of drilling, then screwing into a pedicle.
That is why robotic systems for assisting surgery have been developed, which permit to assist the surgeon and to mechanically ensure accuracy and repeatability of the surgical procedure.
In this context, an additional problem during an operation lies in the management of the anatomical movements of the patient due to his own breathing as well as to his heart beating. In particular, the breathing depends on the activity of the diaphragm generating chest and lung movements contributing to the gas exchanges. This muscular activity causes a deformation of the collateral anatomical parts, such as the abdomen and the rachis. The magnitude of this deformation depends on the minute ventilation (MV), depending on its volume and its frequency, but also on the position of the patient, namely standing, sitting or lying on his stomach, back or side.
In the case of an operation on the rachis, the latter moves to a larger extent for the thoracic vertebrae and to a lesser extent for the lumbar vertebrae. In addition, the movements of a specific vertebra can be modified by the action of the surgeon as part of his operation, namely when he drills or breaks the bone structure, or cuts muscles and ligaments, which also support the vertebral structure.
In order to limit these movements during a lumbar surgery, when the access path permits such, the patient is lying on his stomach, taking care to leave the movements of the belly free below the level of the chest region. The patient is then immobilized in this position by mechanisms and accessories of the operating table. This particular prone position permits to significantly reduce the magnitude of the movements of the lumbar rachis.
However, the breathing and especially the external forces resulting from the operation generate mutually periodic and extemporaneous movements of the lumbar rachis of several millimeters, which the surgeon is then obliged to compensate for thanks to his dexterity and his visual acuity.
In the case of a robotic-assisted operation, it is extremely important to measure these motions for the robotic arm to automatically adjust to these movements, in order to maintain the improved robotic accuracy compared to that of the surgeon, while accompanying said movements with a speed of execution corresponding to the speed of the target.
To this end, in order to be in line with the pre-operative planning on 3D imaging, the movements of the anatomical target, namely the lumbar vertebra, should be measured and compensated for in real time in order to maintain the pinpoint accuracy of the device for assisting in location.
At present, the solution of the marker screwed into the backbone is carried out, namely during navigation. An algorithm then calculates the compensations in the location marker in the image, that is displayed and which are transmitted in real time to the robotic arm. However, this solution still has the disadvantage of being invasive. In addition, the optical recognition of the marker risks to be masked by the practitioner, which pass onto said calculation, generates differences in movement of the robotic arm relative to the anatomical movements thus captured.
Such a solution is described in part in US 2006/142657, which relates to a system comprising a first robotic arm and a second passive arm. Said first arm carries an instrument, namely a surgical instrument, while the second arm is made integral at its distal end with a marker anchored in the bone of the targeted anatomical area. Thus, the movement of the bone induces the movement of the marker that is captured by the passive arm, and then passed onto the robotic arm.
However, without imaging, this solution is limited to the operation of the bone itself and does not permit to compensate for movements of other tissues. In short, the mechanical anchoring in the bone permits to follow the movements of the area.
A non-invasive solution is devised through WO 2007/002926, which describes a robotic system for irradiating tissues for treating cancer. In particular, a radiation emitting source, “LINAC”, is carried by a first robotic arm. A second arm serves only as a support for an ultrasonic probe positioned at the level of anatomical area to be treated and recording images of said area. These images are used for calculating the internal movements of the anatomical area.
However, the position in space of the probe is determined by a separate and additional optical system, which still causes the aforementioned problems.
This document also provides for using markers placed at the level of the anatomical area, directly on the skin. The detection of the movements of these markers permits to determine the external movements of the anatomical area.
In addition, a treatment based on a mathematical modeling is necessary to obtain the relative coordinates for correcting the trajectory of the LINAC, relative to the actually measured internal and external movements of the anatomical area. This calculation takes a significant processing time, making difficult its application in the context of an operation on an anatomical area such as the rachis, and always generates degrees of errors.
Another solution is described in DE 10 2008 022924. An imaging system carried by a robotic arm, referred to as “C-arm”, is capable of performing a series of shots that, upon processing, will permit to display the movement of the targeted anatomical area.
However, the C-arm arm serves only as a support for and for positioning said imaging system, depending on the desired orientation of the shots to be taken. This arm is in no way made to follow said anatomical area in accordance with its movements. In brief, once it has been positioned, the arm remains static or its position is changed, without taking into consideration the movements of the target.
Furthermore, the monitoring of the movement of the area is achieved by markers in the form of pellets, glued to the outer portion of the anatomical area. Again, a separate optical or electromagnetic system permits to capture the movements of said markers and to deduce from same the external movements of said anatomical area. This deduction is performed by a mathematical processing in order to guide another robot, which carries an instrument, namely a surgical instrument.
Another related exemplary solution is mentioned in US 2008/033410, which describes a single robotic arm and a fixed support, initially set, without any movement being possible according to the movements being detected. Indeed, said support comprises tubes connected at their ends by collet fixtures, which keep them integral with respect to each other. In order to adjust their relative positions, it is then necessary to loosen said fixtures, change the orientation, then re-tighten the fixtures.
In addition, once again, this system uses a display by means of a not very accurate additional optical system.